In the field of semiconductor packaging, it is standard in the industry to process only one side of each of several wafers, and then combine the separately processed wafers together in packaging.
For example, a known MEMS fuel cell uses three substrates in the final product. One substrate is a silicon wafer which has the MEMS device and one substrate is a glass plate which has through silicon vias (TSVs) formed therein. Separate processing of the wafers prior to packaging is common because each die component can require processing steps that have significantly different chemical and temperature parameters. For example, a MEMs wafer is processed differently from a wafer supporting TSVs. Even further, each wafer can have different support requirements during processing due to fragility of certain components and the mentioned processing parameters. Once the separate wafers are processed, they are packaged into various final semiconductor products as known in the art.